1. Field of the Invention
The present invention relates to a robot for conveying a substrate, for example, a substrate conveyer robot suitable for use in conveying a semiconductor wafer substrate to place it in a container such as a cassette, and to take it out from the container.
2. Related Art
Conventionally, a wafer substrate conveyer robot of the belt link type has an arm expansion/contraction mechanism with first through third arms, in which the gear ratio of the pulley furnished on the rotation spindle of each arm is 2:1:2. This type of robot conveys the substrate horizontally by the control of only two axes. One of them is a robot advancing/retreating axis R for linearly advancing and retreating the third arm by the belt link mechanism, and the other one is a robot revolving axis xcex8 for revolving the rotary base of the robot. Further, with lifting/lowering of all arms, the robot inserts and removes the substrate to and from the cassette.
In general, a substrate conveyer robot 01 possesses an arm expansion/contraction mechanism composed of three arms 05, 07, 09, and the two control axes, i.e., the robot revolving axis xcex8 and the robot advancing/retreating axis R. As illustrated in FIG. 11, the center of the substrate 030 held by a hand 010 fixed on the third arm 09 advances and retreats along a straight line J0 that passes through the center of a rotary shaft (=a first spindle; this is positioned on the same axis as the robot revolving axis xcex8) of the first arm 05. Thus, the substrate conveyer robot 01 is designed to convey and insert the substrate 030 only into a cassette 032 that is disposed with its face centered on the line J0. Here, the straight line J0 coincides with the robot advancing/retreating axis R.
The cassette 032 is in the shape of a quadrangle, and permits the substrate 030 to be inserted only from one direction perpendicular to the plane of the opening thereof. In the case of the conventional robot with two axes, as illustrated in FIG. 11(a) through FIG. 11(c)), the robot 010 or cassette 032 has been required to be disposed in such a manner that the center line of the cassette 032 perpendicular to the aperture plane passes through the robot revolving axis xcex8 (the pivotal center). A rotation base 03 is rotatable around the robot revolving axis xcex8, so that the third arm 09 can be positioned perpendicular to the front of the cassette 032. The third arm 09 is advanced and retreated linearly along the robot advancing/retreating axis R (the straight line J0), thereby inserting and taking out the substrate 030 to and from the cassette 032. In other words, the control of the rotating movement around the robot revolving axis xcex8 and the control of the advancing and retracting movement along the robot advancing/retreating axis R have been carried out sequentially, not simultaneously.
As described above, most of the conventional robots possessing two control axes, the robot revolving axis xcex8 and the robot advancing/retreating axis R, presumably, do not combine the control of rotation around the robot revolving axis xcex8 with simultaneous control of the advancing and retracting along the robot advancing/retreating axis R. Therefore, the conventional robots could only insert and remove the substrate to and from the cassette that is positioned in a radial manner to (in other words, positioned right in front of) the robot revolving axis xcex8.
Therefore, in order for the robot to control the insertion and removal of the substrate to and from the cassette, even in case the cassette is positioned on an arbitrary straight line deviating from the robot revolving axis xcex8, there was no way to use such a robot other than that disclosed in Japanese Patent Laid-Open No. Hei 11(1999)-33948 Publication. This robot adds one axis to the foregoing two axes (two control axes) to freely control the position and direction of the hand of the last arm in the horizontal plane.
However, the use of the robot disclosed in the above publication requires an extra drive along the additional axis, and at the same time complicates control, thus increasing the cost.
The substrate conveyer robot illustrated in FIG. 11 is a single arm sequence type, having an arm expansion/contraction mechanism composed of three arms operative in a single sequence. However, a double arm sequence type substrate conveyer robot that has (a pair) bilaterally symmetrical arm expansion/contraction mechanisms operative in two sequences has the same problem as described above.
The present invention has been made with a view toward solving the above-described problems of the conventional substrate conveyer robots, and an object of the invention is to provide a substrate conveyer robot that can insert and remove a substrate to and from a container disposed in an arbitrary position and orientation, within an accessible range of the robot hand, with a minimum number of control axes, and at a low production cost.
To accomplish the foregoing object, according to one aspect of the invention, the substrate conveyer robot is provided with a rotatable base 3 rotatably driven by a first motor M1 inside the body of the robot, which has a rotational axis Q, on which a first spindle 4 is located in a state isolated from the rotation of the rotatable base 3, which is coaxial with the rotational axis Q, and is rotatably driven by a second motor M2. One end of a first arm 5 is attached to the first spindle 4 and a second spindle 6 protrudes from the other end of the first arm 5 independent of the rotation of the first arm 5, which is rotated with a gear ratio of 2:1 by way of pulleys and a timing belt inside the first arm 5. One end of a second arm 7 is attached to the second spindle 6 and a third spindle 8 protrudes from the other end of the second arm 7 and is independent of rotation of the second arm 7, which is rotated at a gear ratio of 1:2 by way of pulleys and a timing belt inside the second arm 7. The distance between the first spindle 4 and the second spindle 6 is equal to the distance between the second spindle 6 and the third spindle 8. One end of a third arm 9 is attached to the third spindle 8 and a hand 10 for holding a substrate is firmly attached on the other end of the third arm 9. With the angle of rotation of the rotation base 3 represented by xcex8 and the angle of rotation of the first arm 5 is represented by xcfx86, a control device is provided which controls the angles of rotation xcex8 and xcfx86 in such a manner that the center point of the substrate held by the hand 10, horizontally spaced from the pivotal center Q, moves linearly relative to the body of the robot on the straight line H, in an arbitrary direction within an accessible range of the hand 10, and the substrate is inserted into and removed from a container, while the substrate is being rotated.
The substrate conveyer robot with the above construction is a so-called single arm sequence type substrate conveyer robot having a single sequence arm expansion/contraction mechanism that contains the first through third arms 5, 7, and 9. The control device controls the angle of rotation xcex8 of the rotatable base 3 provided in the body of the robot and the angle of rotation xcfx86 of the first arm 5, in such a manner that the center point of the substrate held by the hand 10, spaced from the pivotal center Q, moves linearly relative to the body of the robot on the straight line H in an arbitrary direction within the accessible range of the hand 10, and the substrate is inserted into and removed from the container, while the substrate is being rotated. Therefore, in contrast to the conventional single arm sequence type substrate conveyer robot, the invention provides a substrate conveyer robot that can insert and remove the substrate to and from the container disposed in an arbitrary position and direction within the accessible range of the hand 10 of the robot, without increasing the number of control axes, at a low production cost.
Further, in the foregoing construction, the control device preferably controls the rotation angles xcex8 and xcfx86 each so as to satisfy:
{m+2L sin(xcfx86)} sin(xcex8)=h(constant),
where it is assumed that the center point of the substrate is spaced from the pivotal center Q by a constant distance h, and moves linearly relative to the body of the robot on the straight line H in an arbitrary direction within the accessible range of the hand 10, and that the distance between the first spindle 4 and the second spindle 6 and the distance between the second spindle 6 and the third spindle 8 are represented by L, and that the distance between the third spindle 8 and the center of the substrate is represented by m. As the result, the combination control of these angles of rotation xcex8 and xcfx86 becomes very simple, with the center point of the substrate held by the hand 10, spaced from the pivotal center Q, moved linearly relative to the body of the robot on the straight line H in an arbitrary direction within the accessible range of the hand 10, and the substrate is inserted into and removed from the container, while being rotated.
According to another aspect of the invention, the substrate conveyer robot is provided with a rotatable base 3 rotatably driven by a first motor M1 inside the body of the robot, which has a pivotal center Q, in which first spindles 4, 4xe2x80x2 are rotatable independent of rotation of the rotatable base 3 and are spaced an equal distance x, symmetrically, from the pivotal center Q. Spindles 4,4xe2x80x2 are rotatably driven by second motors M2, M2xe2x80x2, respectively. First ends of first arms 5, 5xe2x80x2 are respectively attached to the first spindles 4, 4xe2x80x2 and second spindles 6, 6xe2x80x2 protrude from opposite ends of the first arms 5, 5xe2x80x2 and are rotatably driven, independent of the rotation of the first arms 5, 5xe2x80x2 with a gear ratio of 2:1 by way of pulleys and timing belts inside the first arms 5, 5xe2x80x2. First ends of second arms 7, 7xe2x80x2 are attached to the second spindles 6, 6xe2x80x2, respectively and third spindles 8, 8xe2x80x2 are at the opposite ends of the second arms 7, 7xe2x80x2. Third spindles 8, 8xe2x80x2 are rotatably driven, independent of the rotation of the second arms 7, 7xe2x80x2, with a gear ratio 1:2 by way of pulleys and timing belts inside the second arms 7, 7xe2x80x2. The distance between the first spindles 4, 4xe2x80x2 and the second spindles 6, 6xe2x80x2 is equal to the distance between the second spindles 6, 6xe2x80x2 and the third spindles 8, 8xe2x80x2. First ends of third arms 9, 9xe2x80x2 are attached to the third spindles 8, 8xe2x80x2 and hands 10, 10xe2x80x2 for holding substrates are firmly attached on the opposite ends of the third arms 9, 9xe2x80x2. Centers of the substrates held by the hands 10, 10xe2x80x2 are positioned offset radially inward by an equal distance x from the third spindles 8, 8xe2x80x2, and the first spindles 4, 4xe2x80x2 are symmetrically offset radially outward by the distance x from the pivotal center Q. With the angle of rotation of the rotatable base 3 represented by xcex8 and the angles of rotation of the first arms are each represented by xcfx86, xcfx86xe2x80x2, a control device is provided which controls the angles of rotation xcex8 and xcfx86, xcfx86xe2x80x2, in such a manner that center points of the substrates held by the hands 10, 10xe2x80x2, spaced from the pivotal center Q, move linearly relative to the body of the robot along the straight lines H, Hxe2x80x2 in arbitrary directions and within accessible ranges of the hands 10, 10xe2x80x2, and the substrates are inserted into and removed from a container or containers, while being rotated.
The substrate conveyer robot with the above construction is a so-called double arm sequence type substrate conveyer robot having two sequences, i.e., a pair of arm expansion/contraction mechanisms, which contain first through third arms 5, 5xe2x80x2, 7, 7xe2x80x2, and 9, 9xe2x80x2 respectively, in a bilateral symmetry. The control device controls the angle of rotation xcex8 of the rotatable base 3 provided in the body of the robot and the angles of rotation xcfx86, xcfx86xe2x80x2 of the first arms 5, 5xe2x80x2, so that the center points of the substrates held by the hands 10, 10xe2x80x2, offset from the pivotal center Q, move linearly relative to the body of the robot along the straight lines H, Hxe2x80x2 in arbitrary directions, within the accessible ranges of the hands 10, 10xe2x80x2, and the substrates are inserted into and removed from the container(s), while being rotated. Therefore, in contrast to the conventional double arm sequence type substrate conveyer robot, the invention provides a substrate conveyer robot that can insert and remove the substrates to and from the containers disposed in arbitrary positions and directions within the accessible ranges of the hands 10, 10xe2x80x2 of the robot, without increasing the number of the control axes, at a low production cost.
Further, in the foregoing construction, the control device preferably controls the angles of rotation xcex8 and xcfx86, xcfx86xe2x80x2, each so as to satisfy:
{m+2 L sin(xcfx86)} sin(xcex8)=h(constant),
or (m+2L sin (xcfx86xe2x80x2)} sin (xcex8)=hxe2x80x2 (constant),
where it is assumed that the center points of the substrates are offset from the pivotal center Q by constant distances h, hxe2x80x2, and move linearly relative to the body of the robot on the straight lines H, Hxe2x80x2, in arbitrary directions within the accessible ranges of the hands 10, 10xe2x80x2. The distance between the first spindles 4, 4xe2x80x2 and the second spindles 6, 6xe2x80x2, and the distance between the second spindles 6, 6xe2x80x2 and the third spindles 8, 8xe2x80x2 are represented by L, and the distance before the offset between the third spindles 8, 8xe2x80x2 and the centers of the substrates is represented by m. As the result, the combination of control of these angles of rotation xcex8 and xcfx86, xcfx86xe2x80x2 becomes very simple, with the center points of the substrates held by the hands 10, 10xe2x80x2 offset from the pivotal center Q and moved linearly relative to the body of the robot along the straight lines H, Hxe2x80x2 in arbitrary directions within the accessible ranges of the hands 10, 10xe2x80x2, and the substrates are inserted into and removed from the containers, while being rotated.